coaxial wet-spun yarn supercapacitors for high-energy

ARTICLE

Received 11 Oct 2013 | Accepted 28 Mar 2014 | Published 2 May 2014

Coaxial wet-spun yarn supercapacitors forhigh-energy density and safe wearable electronicsLiang Kou1, Tieqi Huang1, Bingna Zheng1, Yi Han1, Xiaoli Zhao1, Karthikeyan Gopalsamy1,

Haiyan Sun1 & Chao Gao1

Yarn supercapacitors have great potential in future portable and wearable electronics because

of their tiny volume, flexibility and weavability. However, low-energy density limits their

development in the area of wearable high-energy density devices. How to enhance their

energy densities while retaining their high-power densities is a critical challenge for yarn

supercapacitor development. Here we propose a coaxial wet-spinning assembly approach to

continuously spin polyelectrolyte-wrapped graphene/carbon nanotube core-sheath fibres,

which are used directly as safe electrodes to assembly two-ply yarn supercapacitors. The yarn

supercapacitors using liquid and solid electrolytes show ultra-high capacitances of 269 and

177 mF cm� 2 and energy densities of 5.91 and 3.84 mWh cm� 2, respectively. A cloth

supercapacitor superior to commercial capacitor is further interwoven from two individual

40-cm-long coaxial fibres. The combination of scalable coaxial wet-spinning technology

and excellent performance of yarn supercapacitors paves the way to wearable and safe

electronics.

DOI: 10.1038/ncomms4754 OPEN

1 MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, 38 ZhedaRoad, Hangzhou 310027, China. Correspondence and requests for materials should be addressed to C.G. (email: [email protected]).

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Supercapacitors are featured by the fast charge/dischargecapacity, long lifecycle, wide range of operating temperaturesand safety, which have been widely applied in the fields of

digital cameras, mobile phones, electrical tools and pulse lasertechniques1,2. Yarn supercapacitors (YSCs) are of particularinterest because of their merits of tiny volume, high flexibilityand weavability, and are promising for the next generation ofwearable electronic devices3,4. Compared with batteries, super-capacitors show much lower-energy density, limiting theirpractical applications. Therefore, it is crucial to enhance theirenergy densities (E) while retaining their intrinsic high specificpower densities (P) for the development of YSCs. Increasing thecharge-storage capability and decreasing the volume of YSCs aretwo main approaches to enhance E. To improve the charge-storagecapability of YSCs, conductive carbon materials with high specificarea such as carbon fibre4, fibres of carbon nanotubes (CNTs)5,graphene3,6 and ordered mesoporous carbon7 were commonlyselected as electrodes, and electrical-active materials with faradaicpseudocapacitance such as metal oxides (for example, MnO2)8 andconducting polymers (for example, polypyrrole9, polyaniline(PANI)5, and poly(3,4-ethylenedioxythiophene, PEDOT)10) weretried to incorporate into/on the electrodes. The capacitance (C) ofYSCs was then enhanced from 2.4 to 86.8 mF cm� 2 in the past3 years4,11; however, the C and E values are still quite low forpractical applications. Alternatively, decreasing the YSC volumeshall be an effective way to increase volumetric E, yet it has a highrisk of short circuit of electrodes.

To date, all of the as-prepared fibres used for fabricating YSCsare naked, and thus are easy to be short-circuited when they areclose to each other3,5. Although post-coating a layer of poly(vinylalcohol) (PVA) solid electrolyte partly reduces the probability ofshort circuit, the coating process is complicated and time-consuming, and it is hard to evenly coat the PVA layer. Theresultant YSCs showed unsatisfied C and low E6. Therefore, it is stilla big challenge to develop a simple yet effective approach to directlyprepare sheath-protected fibre electrodes with ultra-high C and E.

In this work, a coaxial wet-spinning assembly strategy isproposed to readily prepare polyelectrolyte-wrapped carbonnanomaterial (for example, graphene, CNTs and their mixture)core-sheath fibres that are applied directly as contactableand interweaving YSC electrodes without the risk of short circuit.The resulting compact two-ply YSCs show high C and E valuesup to 177 mF cm� 2 (158 F cm� 3) and 3.84mWh cm� 2

(3.5 mWh cm� 3), respectively. C and E are further improvedto 269 mF cm� 2 (239 F cm� 3) and 5.91mWh cm� 2

(5.26 mWh cm� 3) using liquid electrolyte. For the first time, acloth supercapacitor with C higher than commercial capacitor isinterwoven from two individual ultra-long (40 cm) continuouscoaxial fibres. The combination of industrially viable coaxial wet-spinning assembly approach and ultra-high electrochemicalperformance of YSCs paves the way to wearable and safeelectronics.

ResultsCoaxial wet-spinning assembly approach to polyelectrolyte-wrapped graphene fibres. Our group has first demonstrated thatcontinuous graphene fibres could be achieved by wet-spinninggraphene oxide (GO) liquid crystals (LCs)12,13 followed bychemical reduction14,15, opening the door to macroscopic, multi-functional graphene fibres with widely potential applicationsincluding in the area of YSCs6. Recently, other groups alsoconfirmed the fabrication of graphene fibres by either wet-spinning technology16–19 or dimensionally confined hydro-thermal strategy20. The wet-spinning assembly approach wasalso successfully extended to create porous aerogel fibres21,

hollow graphene fibres22 and nacre-mimetic graphene/polymercomposite fibres15,23,24. The resulting graphene fibres are light-weight, electrically conductive, strong, flexible and chemical-resistant, which is promising for practical applications inmultifunctional textiles and wearable electronics. However,despite these efforts in the fabrication of various structuralfibres, all of them are also naked with the risk of short circuitwhen used as electrodes, which is unfavourable for theconstruction of safe electronics such as YSCs.

To solve this problem, we designed a coaxial wet-spinningassembly strategy to prepare polyelectrolyte-wrapped graphenefibres. Although coaxial electrospinning technology has beenutilized to spin core-sheath nanofibres25, coaxial wet-spinningapproach has never been established to prepare coaxialmicrofibres from colloidal nanoparticles because of the extremedifficulty for the selection of desirable coagulation bath as well asharmonious solvents of inner and outer components. Figure 1ashows the schematic illustration of our coaxial wet-spinningprocess (the photograph of corresponding equipment is shown inSupplementary Fig. 1). The spinneret is featured by two inlets thatconnect the inner and outer channels, respectively. We firstselected the aqueous GO LC as the inner spinning dope since itwas easily spun into continuous microfibres according to theestablished wet-spinning assembly protocol. The aqueoussolution of sodium carboxymethyl cellulose (CMC) was chosenas the outer spinning dope because CMC is an ionicallyconductive while electrically insulative polyelectrolyte. Such apolymer sheath ensures fibre electrodes free of short circuit whenintertwined together, while allowing ions to smoothly penetratefrom the electrolyte matrix to electrodes simultaneously.

Typically, the aqueous GO LC from the inner channel andthe CMC aqueous solution from the outer channel weresynchronously injected into the coagulating bath of ethanol/water (5:1 v/v) solution with 5 wt% CaCl2 (ref. 13) Wet CMC-wrapped GO coaxial fibres (GO@CMC) were then shaped rapidly(Fig. 1b), and the magnified photograph (Fig. 1c) showed clearcore-sheath structure as designed. The GO dispersions wereprepared according to the previous protocol15,26,27. Atomic forcemicroscopy demonstrates that GO is a monolayer with thethickness of 0.7 nm (Supplementary Fig. 2). Scanning electronmicroscopy (SEM) images also prove the fine dispersity of GOsheets since no aggregation was observed (Supplementary Fig. 3).The solidification process of GO@CMC fibre was in situ tracedusing polarized-light optical microscopy. Vivid schlieren texturewas found for the core part of GO because of its LC birefringence(Fig. 1d). During the solidification process, the bright texture wasmaintained, indicating the uniform alignment of GO sheetsalong the fibre axis in the shrinkage process (SupplementaryFig. 4). At the same time, the outer black polymer sheathwithout birefringence was well retained until full solidification,demonstrating the continuous core-sheath structure of GO@CMC fibre (Supplementary Fig. 4).

The GO@CMC fibres were chemically reduced by hydroiodicacid14. The colour of the core was then changed from brown(Fig. 1b,c) to dark while the polyelectrolyte sheath retained well(Fig. 1e–g). The chemically reduced GO@CMC fibres(RGO@CMC) were highly conductive with a conductivity ofB7,000 S m� 1 as measured from their naked ends of the core.Such a high conductivity is comparable to that of neat graphenefibres and papers (B7,000–25,000 S m� 1), confirming theintegrity of the inner fibre and thus enabling it to be used as anelectrode of YSCs. On the contrary, the whole fibre was electricallyinsulative as measured from its side face because of the protectionof the insulative polymer sheath (Supplementary Fig. 5). Suchwell-defined sectorization of core-sheath fibre paves the way tosafe assembly of microelectronics. Similar to the wet-spinning of

ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/ncomms4754

2 NATURE COMMUNICATIONS | 5:3754 | DOI: 10.1038/ncomms4754 | www.nature.com/naturecommunications



neat graphene fibres, continuous GO@CMC fibres were obtainedby the coaxial wet-spinning approach, as shown in SupplementaryMovie 1. Consequently, ultra-long coaxial fibres up to 100 m wereachieved (Fig. 1h), showing large-scale productivity of themultifunctional core-sheath fibres. In addition, the CMC sheathwas swollen in ethanol/water (3:1 v/v) solution to colour the fibreswith dyes such as rhodamine B, rendering the fibres colourful(Fig. 1i,j) and fluorescence-emissive (Fig. 1k).

The microscopic morphology of the coaxial fibres wascharacterized using SEM. Figure 2a–c shows typical SEM imagesof a GO@CMC fibre with a GO core of ca. 50mm and a CMCsheath of ca. 25 mm thickness. The GO core is featured by thecompact layered structures with dentate bends, which is similar tothe oriented structures of neat graphene fibres13. The CMCsheath wraps the core tightly without any gaps and voids, which isextremely important for the ion transport when served assupercapacitor electrodes, as evidenced by transmission electronmicroscopy (TEM) images in Supplementary Fig. 6. Diameter ofthe GO core and thickness of the CMC sheath were readilyadjusted by changing either the concentration or outflow velocityof GO and CMC spinning dopes (Fig. 2d–f and SupplementaryFig. 7). After the chemical reduction by hydroiodic acid, thelayered structure of core becomes slightly fluffy and cellular(Fig. 2g–i), which could largely increase the accessible area ofelectrolyte. The coaxial fibres showed ultra-high flexibility withelongation of 8–10% and good mechanical strength (73–116 MPa;Supplementary Fig. 8). This robustness is propitious to their usein woven devices.

Extension of coaxial wet-spinning assembly approach. Besidesgraphene, CNTs were also widely used as electrically conductive

electrodes. Two main protocols have been developed to makemacroscopic CNT fibres: dry drawing of aligned CNTs5 andwet-spinning of surfactant-stabilized CNTs with a coagulationbath of PVA aqueous solution28. However, it is still hard todirectly wet-spin neat CNTs in the absence of surfactants orpolymers because of their relatively poor dispersibility. In thispaper, we realized the continuous wet-spinning of neat CNTsvia the as-established coaxial spinning assembly approach(Supplementary Movie 2). Likewise, as the inner component ofCNT dispersions was co-injected with the outer componentof CMC dope into the coagulation bath, continuous CMC-wrapped CNT fibres (CNT@CMC) were produced. Thisprocess is similar to the coaxial electrospinning of nanoparticleswithout spinnability25. Figure 2j–l shows typical features ofCNT@CMC fibres. The thickness of the sheath is 2–5 mm and thediameter of the CNT core is ca. 50mm. The CNT core is compactwithout any voids, and the CNTs are also oriented along the fibreaxis because of the shear stress of wet-spinning in the spinneretcapillary.

We further extended the coaxial wet-spinning assemblyapproach to prepare continuous coaxial fibres with the core ofmixture of RGO and CNTs, denoted as RGOþCNT@CMC(Fig. 2m–o). CNTs were coated on the surfaces of RGO denselyand separated the adjacent RGO sheets aligned with layeredstructures (Fig. 2o). The coating of CNTs on RGO sheets greatlyincreases the specific area of the fibres, which is beneficial toenergy storage when used as YSC electrodes. Moreover, replacingthe outer layer of CMC by GO dispersion, we also prepared all-carbon RGOþCNT@RGO core-sheath fibres (SupplementaryFig. 9). Therefore, our coaxial wet-spinning assembly strategy isuniversal and versatile to create designed, multifunctional core-sheath fibres.

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Figure 1 | Coaxial wet-spinning assembly process and the as-prepared core-sheath fibres. (a) Schematic illustration showing the coaxial spinning

process. (b) A single intact wet GO@CMC fibre and its magnified image (c). (d) Polarized-light optical microscopy image of wet GO@CMC fibre

indicating the core-sheath structure and the well-aligned GO sheets in the core part. (e) A wet RGO@CMC fibre and its magnified images with blue (f) and

black (g) backgrounds. (h) The macroscopic photo of the RGO@CMC coaxial fibres. Wet (i) and dry (j) coaxial fibres dyed by rhodamine B and its

fluorescence photos (k) in the dark under UV irradiation. Scale bars, 1 cm (b,e), 5 mm (c,f,g), 100mm (d) and 2 mm (i–k).

NATURE COMMUNICATIONS | DOI: 10.1038/ncomms4754 ARTICLE




Coaxial fibres assembled two-ply YSCs. Given the uniqueattributes of the core-sheath coaxial fibres, we directly usedthem as safe electrodes for making two-ply YSCs. The YSCs wereprepared by tightly intertwining two coaxial fibres followed bycoating a layer of H3PO4-PVA gel electrolyte as ion source(Fig. 3a,b)8. The as-prepared YSCs are very safe, and short circuitnever happened in the assembly and working process ofYSCs because of the protection of the CMC sheath. The cross-sectional view of the YSC shows that the coaxial structureof the fibre electrodes is well reserved (Fig. 3a). The H3PO4-PVAgel electrolyte was coated on the coaxial fibre electrodes tightlyand penetrated into the gap between them, which is important forthe high capacitance performance of YSCs. The side view of theYSC indicates the uniform coating of PVA electrolyte and theclearly intertwined morphology of the two fibres (Fig. 3b).Significantly, the two-ply YSC is flexible enough to make a

compact knot and the two fibre electrodes are observed along theYSC (Fig. 3c).

We first assembled two kinds of two-ply YSCs with neatgraphene (RGO@CMC) and neat CNT (CNT@CMC) coaxialfibres, respectively, to testify the feasibility of our strategy. Theelectrochemical properties of the as-prepared YSCs werecharacterized by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements. For the YSCs intertwinedwith RGO@CMC fibres, the CV curves show a nearly rectangularshape and a rapid current response to voltage reversal at each endpotential (Fig. 3d), which illustrates the good electrochemicalperformance of the YSCs. Figure 3g shows the GCD behaviour ofRGO@CMC YSCs between 0 and 0.8 V at different currentdensities (0.1–1.0 mA cm� 2). The GCD curves are close totriangular shape, confirming the formation of an efficient electricdouble layers and good charge propagation across the two fibre

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Figure 2 | SEM images of coaxial fibres. (a–c) GO@CMC spun with GO of 20 mg ml� 1 and CMC of 12 mg ml� 1. (d–f) GO@CMC spun with GO of

20 mg ml� 1 and CMC of 4 mg ml� 1. (g–i) RGO@CMC spun with GO of 20 mg ml� 1 and CMC of 8 mg ml� 1. (j–l) CNT@CMC spun with CNT of

10 mg ml� 1 and CMC of 8 mg ml� 1. (m–o) RGOþCNT@CMC spun with GO and CNT mixture (w/w, 1/1) of 20 mg ml� 1 and CMC of 8 mg ml� 1.

Scale bars, 20mm (a,d,g,j,m), 10mm (b,h,n), 5 mm (e,k), 2 mm (c,f,i) and 0.2 mm (l,o).





electrodes29. Gram capacitance does not provide a suitable basis forcomparison in YSCs30. Instead, for the convenience of comparingwith the previous results, areal capacitance (CA), length capacitance(CL) and volume capacitance (CV) are commonly utilized toevaluate the charge-storage capacity of YSCs (Table 1; note: thecapacitances denote those of single electrodes). Calculated fromthe GCD curves (Fig. 3g), CAs of RGO@CMC YSCs are extremelyhigh with capacitance of 127 mF cm� 2 (114 F cm� 3 for CV,3.8 mF cm� 1 for CL) at the current density of 0.1 mA cm� 2. Sucha capacitance is two orders of magnitude higher than those ofprevious graphene YSCs3.

For CNT@CMC YSCs, the CV curves also show the desiredrectangular dependence of current density on applied potentialbecause of fast ion transportation (Fig. 3e). The GCD curves exhibita relatively high potential drop (Fig. 3h), which is likely stemmedfrom the larger resistance of carboxylic CNTs. Nevertheless,CNT@CMC YSCs still showed a CA 47 mF cm� 2 (CV 42 F cm� 3,CL 1.4 mF cm� 1) at the current density of 0.1 mA cm� 2, around20 times higher than that of previous neat CNT YSCs5.

The two cases of RGO@CMC and CNT@CMC YSCs efficientlydemonstrate that the polyelectrolyte sheath not only endows thefibre electrodes’ safety (free of short circuit when directly

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Figure 3 | Two-ply YSCs and their electrochemical properties. SEM images of cross-sectional (a) and side (b) view of a two-ply YSC. The arrow area in a

is PVA/H3PO4 electrolyte and inset of b shows the schematic illustration of YSC. (c) SEM image of a two-ply YSC knot. CV curves of RGO@CMC (d),

CNT@CMC (e) and RGOþCNT@CMC (f), scan rates increased from 10 to 20, 50, 80, 100, 150 and 200 mVs� 1. GCD curves of RGO@CMC (g),

CNT@CMC (h) and RGOþCNT@CMC (i), current density increased from 0.1 to 0.2, 0.5, 0.8 and 1 mA cm� 2. (j) Dependence of CA and CV on the

charge/discharge current density for RGO@CMC (3, 4), CNT@CMC (5, 6) and RGOþCNT@CMC (1, 2) YSCs. We selected five cross-sections and used

the average value as the cross-sectional areas to determine the error bars. (k) Nyquist plots of RGO@CMC, CNT@CMC and RGOþCNT@CMC YSCs.

(l) Normalized capacitance (C/C0, where C0 is the initial capacitance) versus cycle number for RGO@CMC (left), CNT@CMC (middle) and

RGOþCNT@CMC (right) YSCs. Scale bars, 50mm (a), 500mm (b), 200mm (c), 3mm for left and 0.3 mm for middle and right (l).





entangled together) but also remarkably improves theperformance of YSCs. Therefore, the creation of coaxial fibresupercapacitors gives brand-new insight for the design andoptimization of YSCs and other electronic devices.

Furthermore, the capacitance of supercapacitors at highcharge–discharge current density is also crucial for their practicalapplication as energy-storage devices. We also tested the charge–discharge performance at different current densities for thecoaxial fibre YSCs. As shown in Fig. 3j, the CAs of RGO@CMCYSCs decreased quickly from 127 to 30 mF cm� 2 as the currentdensity increased from 0.1 to 0.5 mA cm� 2, and then decreasedgradually to 10 mF cm� 2 at the current density of 1.0 mA cm� 2.Even so, the CA values are still quite high at the high currentdensities as compared with the previous neat graphene fibre-based YSCs (1.2 mF cm� 2 at current of 2 mA). The considerabledifference of capacitance between low and high current densitiespartly counteracts the high potential of RGO@CMC YSCs. Bycontrast, the CNT@CMC YSCs showed very stable CA and stillkept 57% of capacitance as the current density increased from 0.1to 1 mA cm� 2 (Fig. 3j), likely because of the smooth ion access inthe porous structures of CNTs.

A question is then raised: is it possible to access ideal YSCswith both features of large CA and high rate capability by thesynergistic assembly of graphene and CNTs?

Ultra-high performance of RGOþCNT@CMC YSCs. Toexploit such a kind of desired YSCs, we also fabricated YSCs withthe electrodes of RGOþCNT@CMC coaxial fibres. The fibrescontained the electrically conductive core assembled homo-geneously by RGO and CNTs (Fig. 2o). Interestingly, theRGOþCNT@CMC YSCs showed much larger area circled byrectangular shaped CV curves (Fig. 3f) and more regular trian-gular shaped GCD curves (Fig. 3i). The discharge time ofRGOþCNT@CMC YSCs reached 700 s at the current density of0.1 mA cm� 2, almost equal to the sum of those of RGO@CMC(497 s) and CNT@CMC YSCs (174 s), indicating the prominentenhancement of stored charges (or capacitance) for thesynergistically assembled electrodes of RGOþCNTs. Hence,the RGOþCNT@CMC YSCs demonstrated much betterelectrochemical performance with CA of 177 mF cm� 2

(CV 158 F cm� 3 and CL 5.3 mF cm� 1) at the current density of0.1 mA cm� 2. This CA value is obviously higher than either CA ofCNT@CMC YSCs or that of RGO@CMC YSCs, approximatingthe total capacitance of the two YSCs (127þ 47 mF cm� 2) under

the same testing condition. This result suggests that a singledevice of RGOþCNT@CMC YSC corresponds to the parallelconnection of one RGO@CMC YSC and one CNT@CMC YSC.The capacitance of RGOþCNT@CMC YSC can be furtherhighly improved to 269 mF cm� 2 (CV 239 F cm� 3 and CL

8.0 mF cm� 1) by using liquid electrolyte of 1 M H2SO4 aqueoussolution (Supplementary Fig. 10). More significantly, theRGOþCNT@CMC YSCs also inherited the high rate capabilitymerit of CNT@CMC YSCs and exhibited high retention (75%) ofcapacitance at a high current density of 1 mA cm� 2 (Fig. 3j).Accordingly, ideal YSCs with both natures of ultra-highcapacitance and excellent rate capability are achieved by thecombination of coaxial wet-spinning assembly approach and thesynergistic effect of graphene and CNTs.

The superior electrochemical performance of RGOþCNT@CMCYSCs can be also explained by the smaller intrinsic internalresistance (R) measured from corresponding electrochemicalimpedance spectroscopy (Fig. 3k). RGOþCNT@CMC YSCs hada smaller R (0.55 KO) than RGO@CMC (0.87 KO) and CNT@CMCYSCs (11.22 KO) on the real axis at high frequency. Moreover,RGOþCNT@CMC YSCs showed a relatively short 45� Warburgregion at the middle frequency, and a more vertical line at lowfrequency, indicating much better electrochemical performance31.

For comparison, we summarized the CA, CV and CL values ofour and the previously reported YSCs in Table 1. Generally, forour YSCs with solid electrolyte of H3PO4/PVA, the CA

(177 mF cm� 2) based on the coaxial fibres is higher than thoseof the ever best YSCs (73 and 86.8 mF cm� 2) by about 100% andis one to three order of magnitude higher than those of commonYSCs (0.4–38 mF cm� 2) even containing the additional electri-cally active materials such as metal oxides and conductivepolymers32,33. The CL of our YSCs (5.3 mF cm� 1) is comparableto the ever highest value (6.3 mF cm� 1) and is one to three orderof magnitude higher than those of other YSCs (0.0114–0.504 mF cm� 1)1,33. Besides, CV of our YSCs is 158 F cm� 3,which is comparable to that of CNT/PEDOT YSCs (179 Fcm� 3)10. For our YSCs with liquid electrolyte of 1 M H2SO4

aqueous solution, CV is improved to 239 F cm� 3, which isobviously higher than that of CNT/PEDOT YSCs with liquidelectrolyte (B167 F cm� 3).

In addition, all these three kinds of YSCs showed almost nodecay of capacitance within 2,000 times of charge–dischargecycles (Fig. 3l) over the range from 0 to 0.8 V at a current densityof 1 mA cm� 2. Leakage current was also measured by chargingYSCs to 0.8 V and keeping them for 2 h (Supplementary Fig. 11).

Table 1 | Comparison of our YSCs with the reported YSCs in terms of C and E.

Ref. Electrode materials C E

CA (mF cm� 2) CV (F cm� 3) CL (mF cm� 1) EA (lWh cm� 2) EV (mWh cm� 3)

This study RGOþCNT 177 158 5.3 3.84 3.51 Pen ink 26.4 1.008 2.73 Graphene 1.7 0.175 PANI/CNT 387 CNT/OMC 39.7 1.91 1.778 CNT/MnO2 3.01 0.015 1.7310 PEDOT/CNT 73 179 0.47 1.411 ZnO nanowires/MnO2 2.4 0.04 0.02731 CNT and Ti fibres 0.6 0.024 0.1532 Graphene 0.726 0.0133 ZnO nanowires/graphene 2 0.02538 PANI/stainless steel 41 0.9539 Carbon/MnO2 2.5 0.22

CNT, carbon nanotube; OMC, ordered mesoporous carbon; PANI, polyaniline; PEDOT, poly(3,4-ethylenedioxythiophene); YSC, Yarn supercapacitor.





The current quickly stabilizes at 0.8 mA, which is essentially theleakage current through the device, indicating a small leakagecurrent and high stability of our YSCs. Such excellent stability iscompetitive in the practical applications of YSCs.

Flexibility and connections of two-ply YSCs. Unlike the liquidelectrolyte with the risk of electrolyte leakage, our all-solid-stateflexible YSCs are highly flectional and were even tied into a knot(Fig. 3c). We tested the GCD curves of the two-ply YSCs underdifferent bending angles (for example, 45�, 90� and 180�), asshown in Fig. 4a. Almost no change for the charge–dischargecurves was observed during the bending, proving that the innerstructures of YSCs maintained well even at a sharp bending state.The coaxial fibre YSCs are flexible and robust enough to toleratethe long-term and repeated bending, and the capacitance onlydropped 2% at 200 times of bending and rose persistently up to111% at 1,000 times of bending (Fig. 4b).

Owing to the flexibility of our two-ply YSCs, we further madetheir serial and parallel connections to control over the operatingvoltage and current. With almost the same discharge time, theoperating voltage can be elevated from 0.8 V for single YSC to 1.6and 2.4 V by connecting two and three YSCs in series, respectively(Fig. 4c). The output currents of two and three YSCs connected inparallel are doubled and tripled, respectively, with a samepotential window of 0–0.8 V (Fig. 4d).

Coaxial fibre-woven cloth supercapacitors. The integration ofhigh flexibility and scalable fabrication of our coaxial fibres

promises highly potential application in garment devices, bio-medical and antimicrobial textiles, and personal electronics34.Figure 5a shows a co-woven cloth using multiple cotton yarnsand two intact coaxial fibres. The fibres are flexible enough toshuttle back and forth without fracture, as demonstrated by theoptical microscopy image of the co-woven cloth (Fig. 5b). For thefirst time, we used two individual 40-cm-long coaxialRGOþCNT@CMC fibres as anode and cathode to interweavea cloth supercapacitor (Fig. 5c,d). Previously, multiple shortCNT/PANI fibres were woven into a piece of cloth, but noelectrochemical property was evaluated5; one two-plysupercapacitor (5 cm long) was straightly drawn across a cottongrove, but no interweaving of two electrodes was demonstrated10.In other words, cloth supercapacitors interwoven from individualintact fibre electrodes have never been reported. In our case, shortcircuit of the fibre electrodes was avoided at the crossing of thecloth because of the unique coaxial insulated polyelectrolyte-wrapped structure. Our cloth supercapacitor showed acapacitance of 28 mF at the current of 10 mA (Fig. 5e), higherthan 25 mF of commercial supercapacitors35. The correspondingGCD curves were unchanged under the bending angle of 180�along the three directions shown in the inset of Fig. 5e, revealingthe excellent bendability of our cloth supercapacitors woven fromcoaxial fibres.

DiscussionAs shown above, our two-ply YSCs possess the various merits ofultra-high capacitance, good rate capability, excellent cycling

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Figure 4 | The capacitance performance of YSCs under bending and series/parallel connections. (a) GCD curves of two-ply, all-solid-state, free-

standing YSCs bended with different angles at the current density of 0.1 mA cm� 2, and the insets are the digital photos of YSCs with different bending

angles. (b) Capacitance ratio (C/C0, where C0 is the initial capacitance) versus bending times for YSCs with bending angles of 180�. (c) GCD

curves of single, two and three YSCs connected in series, and the insets depict the cartoon of the YSCs connected in series. (d) CV curves of single, two

and three YSCs connected in parallel, and the insets show the corresponding schematics (scan rates, 10 mVs� 1).





stability, high flexibility and knittability, and fine modulability ofconnection. Besides, E and P of supercapacitors are also quiteimportant parameters for their real applications3,4,36. We thendraw the profile of P versus E, so-called Ragone plot37, derivedfrom GCD curves at various current densities from 0.1 to1 mA cm� 2 for the RGOþCNT@CMC YSCs (Fig. 6a). As aresult, the YSC using solid electrolyte shows areal energy density(EA) of 3.84 mWh cm� 2 and volumetric energy density (EV) of3.5 mWh cm� 3, while the areal power density (PA) andvolumetric power density (PV) is 0.02 mW cm� 2 and0.018 W cm� 3 at the current density of 0.1 mA cm� 2,respectively.

Notably, as far as we know, our EA value is the highest energydensity for all of reported YSCs (Table 1). As a quantitativecomparison, it corresponds to 142 times of YSC based on ZnOnanowires/MnO2 (0.027 mWh cm� 2)11, 26 times of YSC based onCNT and Ti fibres (0.15 mWh cm� 2)31, 22 times of YSC based on

core-sheath graphene fibres (0.17mWh cm� 2)3, 4 times of YSCbased on PANI/stainless steel (0.95 mWh cm� 2)38, 2.17 timesof YSC based on CNT/ordered mesoporous carbon(1.77 mWh cm� 2)7 and 1.42 times of YSC based on pen ink(2.7 mWh cm� 2)1. Alternatively, EV of RGOþCNT@CMC YSCsis 3.5 mWh cm� 3, around 16 times of YSC based on carbon/MnO2 (0.22 mWh cm� 3)39 and two times of YSC based onCNT/MnO2 fibres (1.73 mWh cm� 3)8.

The excellent electrochemical performance of our YSCs islikely resulted from three effects. First, during coagulation anddrying process for the coaxial wet-spinning technology, theshrinkage speed of the outer CMC layer is faster than that of theinner GO or CNTs core, making CMC sheath wrap the grapheneor CNTs tightly (Supplementary Fig. 6). This is crucial for betterion transport at the interface between electrolyte and theelectrodes. Second, this coaxial wet-spinning process rendersthe pore structures of inner GO or CNTs core more elaborate

i

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Figure 5 | Supercapacitor based on the cloth woven by coaxial fibres. (a) Two intact coaxial fibres woven with cotton fibres. (b) Optical macroscopic

image of a. (c) Cloth woven by two individual coaxial fibres. (d) Supercapacitor device based on the cloth fabricated by two coaxial fibres (denoted

as i and ii, respectively). (e) GCD curves of the cloth supercapacitor (1 represents initial cloth supercapacitor without bending, and 2, 3, 4 show cloth

supercapacitor with bending angles of 180� along three directions). Scale bars, 1 cm (a) and 200mm (b).

0 200 400 600 800 1,000 1,200 1,400

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h cm–2)

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Figure 6 | Volumetric and areal energy versus average power densities and the shell thickness effect for RGOþCNT@CMC YSCs. (a) Ragone plots

compared with the selected previous fibre-shaped YSCs with solid electrolyte. (b) GCD curves at the current density of 0.1 mA cm� 2 for

RGOþCNT@CMC fibres with CMC shell thickness of 0 mm (1), 2 mm (2), 10mm (3) and 25mm (4).





lenovo

高亮

because of the uniform shrinkage force of the CMC sheath.The thicker the CMC sheath is, the stronger the shrinkage forcewould be generated during the drying process. Therefore, the CA

of RGOþCNT@CMC YSCs increased from 35 to 103, 145 and177 mF cm� 2 with increasing the thickness of CMC sheath from0 (Supplementary Fig. 12) to 2, 10 and 25 mm (SupplementaryFig. 13). To further demonstrate the merits of the coaxial wet-spinning assembly strategy, we assembled two more YSCs incontrol experiments using naked RGOþCNT fibres fabricated byconventional wet-spinning method12 and RGOþCNT fibrespost-coated with CMC as electrodes, respectively. After post-coating a CMC layer on the surface of naked RGOþCNT fibres,the capacitance (39 mF cm� 2) is almost same as that of the initialnaked RGOþCNT fibre without CMC coating (35 mF cm� 2)but much smaller than that of coaxial wet-spun fibres(103 mF cm� 2) at the current density of 0.1 mA cm� 2. The CVcurves of CMC post-coating YSC and naked fibre YSC are almostoverlapped, whereas much smaller than those of coaxial wet-spunfibre YSC (Supplementary Fig. 14e). These control experimentsclearly demonstrated that CMC has no pseudocapacitance effectand the dramatic improvement of electrochemical performancefor coaxial wet-spun fibre-based YSCs is mainly ascribed to thecoaxial wet-spinning assembly process. Meanwhile, the ratecapability is also excellent for the coaxial wet-spun fibre YSCs.For RGOþCNT@CMC YSCs with CMC thickness of 2, 10 and25 mm, the capacitances are retained by 84%, 77% and 75%,respectively, when the current density is increased from 0.1 to1 mA cm� 2 (Supplementary Fig. 13). The slightly different ratecapability is likely caused by the increased thickness of CMC,which might lead to a longer distance between the two fibreelectrodes. As a result, ion transport is affected to some extent athigh current densities. Finally, the synergistic effect that arosefrom the hierarchical structures of CNT-coated graphene makesthe C and E of RGOþCNT@CMC YSC superior to either RGO@CMC or RGOþCNT@CMC YSC. Therefore, the combinationof the coaxial wet-spinning process and the hierarchicalstructures of CNT-coated graphene mainly contributes to thehigh performance of RGOþCNT@CMC YSCs.

In conclusion, we proposed and demonstrated for the first timea coaxial wet-spinning assembly strategy to prepare core-sheathfibres of polymer-wrapped carbon nanomaterials. The protocol issimple, industrially viable and general for both nanoparticles ofgraphene and CNTs that cannot be wet-spun continuously byprevious approaches. The as-made coaxial fibres are flexible androbust enough to be intertwined, knotted and woven. Owing tothe coating of electrically insulative polyelectrolyte, the coaxialfibres were used directly to assembly two-ply intertwined safeYSCs. The resultant RGOþCNT@CMC YSCs showed ultra-highcapacitance, the record energy density and excellent cycle stabilityunder bending. A highly bendable cloth supercapacitor waswoven from two 40-cm-long coaxial fibres, promising theapplication of our YSCs in garment devices, intelligent micro-sensors and other wearable electronics. The electrically activemetal oxides (for example, MnO2, NiO and RuO2) andconductive polymers can widely be integrated into the coaxialfibres to further improve the electrochemical performance ofYSCs40, offering a wide approach to the next generation of smart,safe and flexible devices.

MethodsPreparation of coaxial fibres by coaxial wet-spinning. GO and CNT dispersionswere prepared according to the previous reports41–44. For preparing RGO@CMC,GO dispersion was concentrated to B20 mg ml� 1 and transferred to an injectionsyringe connected with an inner core of spinneret. CMC (Aladdin) dissolved inwater with concentration of B8 mg ml� 1 was transferred to the outer channel ofspinneret. The typical extruded velocities of inner and outer layers were set at10 and 40ml min� 1, respectively. The coagulating bath was ethanol/water (5:1 v/v)

solution with 5 wt% CaCl2. After coagulation for 30 min, the fibres were immersedin hydriodic acid ethanol/water (5:1 v/v) solution for 1 h at 95 �C for reductionfollowed by ethanol washing and drying in air, affording RGO@CMC coaxialfibres. The CNT@CMC coaxial fibres were prepared with the same procedure byreplacing GO with CNT aqueous dispersions. Likewise, for spinningRGOþCNT@CMC coaxial fibres, GO and CNT dispersions were first mixed withweight ratio of 1/1 by magnetic stirring for 2 h and then were used as the innerspinning dope.

Preparation of PVA solid electrolyte. Water (10 ml) and phosphoric acid (10 ml)were mixed by magnetic stirring for 30 min in a 250-ml glass bottle. PVA (10 g, Mw89,000–98,000) dissolved in 90 ml water at 90 �C was added in the above solutionand was kept stirring for 1 h.

Preparation of free-standing all-solid-state fibre supercapacitors. Two coaxialfibres were twisted together to form two-ply supercapacitor electrodes. They werethen coated with PVA electrolyte by dip-coating method and solidification at 40 �C.

Apparatus for characterizations. Atomic force microscopy images were taken inthe tapping mode by carrying out on a NSK SPI3800. SEM images were taken on aHitachi S4800 field-emission SEM system. The core-sheath fibre was cut into slicesby microtome and observed by TEM (FEI-PHILLIPS CM 200 electron micro-scope). Polarized-light optical microscopy observations were performed with aNikon E600POL. CV, electrochemical impedance spectroscopy and GCD mea-surements were performed using an electrochemical workstation (CHI660e, CHInstruments Inc.). The tensile stress–strain tests were performed on a Micro-computer Control Electronic Universal Testing Machine made by REGER in China(RGWT-4000-20).

Calculation of the electrochemical capacitance for two-ply electrode super-capacitors. The two-ply YSC is a symmetric two-electrode solid-state super-capacitor. The areal capacitance (CA) was derived from the equation:CA¼ I� t�U� 1� S� 1, where I stands for discharge–discharge current, t is thedischarge time, U represents the potential window and S is the surface area of singleyarn in the overlapping portion, equal to the circumference of the cross-sectionmultiplied by the length (L) of overlapped portion of fibre electrodes5.Circumference is measured by using a soft rope walked along the cross profileof the SEM images of the fibres. CV was derived from the equation:CV¼CA� S�V� 1. V is the volume of the fibre electrode, which is equal tothe cross-sectional area multiplied by the length of overlapped portion of fibreelectrodes. Cross-sectional areas are measured through Photoshop (image-processing software) by comparing the pixel with that of an internal reference. Thelength capacitance CL was derived from the equation: CL¼CA� S� L� 1. Theareal energy density (E) and areal power density (P) of the YSCs can be obtainedfrom EA¼ 0.125�CA�U2 and PA¼EA� t� 1. The volumetric energy density (E)and volumetric power density (P) of the YSCs can be obtained fromEV¼ 0.125�CV�U2 and PV¼ EV� t� 1.

References1. Fu, Y. et al. Fibre supercapacitors utilizing pen ink for flexible/wearable energy

storage. Adv. Mater. 24, 5713–5718 (2012).2. Wang, G., Zhang, L. & Zhang, J. A review of electrode materials for

electrochemical supercapacitors. Chem. Soc. Rev. 41, 797–828 (2012).3. Meng, Y. et al. All-graphene core-sheath microfibres for all-solid-state,

stretchable fibriform supercapacitors and wearable electronic textiles. Adv.Mater. 25, 2326–2331 (2013).

4. Le, V. T. et al. Coaxial fibre supercapacitor using all-carbon material electrodes.ACS Nano 7, 5940–5947 (2013).

5. Wang, K., Meng, Q., Zhang, Y., Wei, Z. & Miao, M. High-performance two-plyyarn supercapacitors based on carbon nanotubes and polyaniline nanowirearrays. Adv. Mater. 25, 1494–1498 (2013).

6. Huang, T. et al. Flexible, high performance wet-spun graphene fibersupercapacitors. RSC Adv. 3, 23957–23962 (2013).

7. Ren, J. et al. Flexible and weaveable capacitor wire based on a carbonnanocomposite fiber. Adv. Mater. 25, 5695–5670 (2013).

8. Ren, J. et al. Twisting carbon nanotube fibres for both wire-shaped micro-supercapacitor and micro-battery. Adv. Mater. 25, 1155–1159 (2013).

9. Tao, J. et al. Solid-State High performance flexible supercapacitors based onpolypyrrole-MnO2-carbon fibre hybrid structure. Sci. Rep. 3, 2286 (2013).

10. Lee, J. A. et al. Ultrafast charge and discharge biscrolled yarn supercapacitorsfor textiles and microdevices. Nat. Commun. 4, 1970 (2013).

11. Bae, J. et al. Fibre supercapacitors made of nanowire-fibre hybrid structuresfor wearable/flexible energy storage. Angew. Chem. Int. Ed. 50, 1683–1687(2011).

12. Xu, Z. & Gao, C. Graphene chiral liquid crystals and macroscopic assembledfibres. Nat. Commun. 2, 571 (2011).





13. Xu, Z., Sun, H., Zhao, X. & Gao, C. Ultrastrong fiber assembled from giantgraphene oxide sheets. Adv. Mater. 25, 188–193 (2013).

14. Pei, S., Zhao, J., Du, J., Ren, W. & Cheng, H.-M. Direct reduction of grapheneoxide films into highly conductive and flexible graphene films by hydrohalicacids. Carbon. 48, 4466–4474 (2010).

15. Kou, L. & Gao, C. Bioinspired design and macroscopic assembly of poly(vinylalcohol)-coated graphene into kilometers-long fiber. Nanoscale 5, 4370–4378(2013).

16. Jalili, R. et al. Scalable one-step wet-spinning of graphene fiber and yarns fromliquid crystalline dispersions of graphene oxide: towards multifunctionaltextiles. Adv. Funct. Mater. 23, 5345–5354 (2013).

17. Cong, H.-P., Ren, X.-C., Wang, P. & Yu, S.-H. Wet-spinning assembly ofcontinuous, neat, and macroscopic graphene fibers. Sci. Rep. 2, 613 (2012).

18. Chen, L. et al. Toward high performance graphene fibers. Nanoscale 5,5809–5815 (2013).

19. Xu, Z., Liu, Z., Sun, H. & Gao, C. Highly electrically conductive Ag-dopedgraphene fibers as stretchable conductors. Adv. Mater. 25, 3249–3253 (2013).

20. Dong, Z. et al. Facile fabrication of light, flexible and multifunctional graphenefibers. Adv. Mater. 24, 1856–1861 (2012).

21. Xu, Z., Zhang, Y., Li, P. & Gao, C. Strong, conductive, lightweight, neatgraphene aerogel fibers with aligned pores. ACS Nano 6, 7103–7113 (2012).

22. Zhao, Y. et al. Large-scale spinning assembly of neat, morphology-defined,graphene-based hollow fibres. ACS Nano 7, 2406–2412 (2013).

23. Hu, X., Xu, Z. & Gao, C. Multifunctional, supramolecular, continuous artificialnacre fibres. Sci. Rep. 2, 767 (2012).

24. Liu, Z., Xu, Z., Hu, X. & Gao, C. Lyotropic liquid crystal of polyacrylonitrile-grafted graphene oxide and its assembled continuous strong nacre-mimeticfibres. Macromolecules 46, 6931–6941 (2013).

25. Sun, Z., Zussman, E., Yarin, A. L., Wendorff, J. H. & Greiner, A. Compoundcore-sheath polymer nanofibres by co-electrospinning. Adv. Mater. 15,1929–1932 (2003).

26. Kou, L. & Gao, C. Making silica nanoparticle-covered graphene oxidenanohybrids as general building blocks for large-area superhydrophiliccoatings. Nanoscale 3, 519–528 (2011).

27. Kou, L., He, H. & Gao, C. Click chemistry approach to functionalize two-dimensional macromolecules of graphene oxide nanosheets. Nano Micro. Lett.2, 177–183 (2010).

28. Vigolo, B. et al. Macroscopic fibres and ribbons of oriented carbon nanotubes.Science 290, 1331–1334 (2000).

29. Yoo, J. J. et al. Ultrathin planar graphene supercapacitors. Nano Lett. 11,1423–1427 (2011).

30. Gogotsi, Y. & Simon, P. True performance metrics in electrochemical energystorage. Science 334, 917–918 (2011).

31. Chen, T. et al. An integrated ‘energy wire’ for both photoelectric conversionand energy storage. Angew. Chem. Int. Ed. 51, 11977–11980 (2012).

32. Li, Y., Sheng, K., Yuan, W. & Shi, G. A high-performance flexible fibre-shapedelectrochemical capacitor based on electrochemically reduced graphene oxide.Chem. Commun. 49, 291–293 (2013).

33. Bae, J. et al. Single-fiber-based hybridization of energy converters and storageunits using graphene as electrodes. Adv. Mater. 23, 3446–3449 (2011).

34. Jost, K. et al. Carbon coated textiles for flexible energy storage. Energ. Environ.Sci. 4, 5060–5067 (2011).

35. Pech, D. et al. Ultrahigh-power micrometre-sized supercapacitors based ononion-like carbon. Nat. Nanotech. 5, 651–654 (2010).

36. Zhai, Y. et al. Carbon materials for chemical capacitive energy storage. Adv.Mater. 23, 4828–4850 (2011).

37. Service, R. F. New ‘supercapacitor’ promises to pack more electrical punch.Science 313, 902 (2006).

38. Fu, Y. et al. Integrated power fibre for energy conversion and storage. Energ.Environ. Sci. 6, 805–812 (2013).

39. Xiao, X. et al. Fibre-based all-solid-state flexible supercapacitors for self-powered systems. ACS Nano 6, 9200–9206 (2012).

40. Simon, P. & Gogotsi, Y. Materials for electrochemical capacitors. Nat. Mater. 7,845–854 (2008).

41. He, H. & Gao, C. General approach to individually dispersed, highly soluble,and conductive graphene nanosheets functionalized by nitrene chemistry.Chem. Mater. 22, 5054–5064 (2010).

42. Kan, L., Xu, Z. & Gao, C. General avenue to individually dispersed grapheneoxide-based two-dimensional molecular brushes by free radical polymerization.Macromolecules 44, 444–452 (2010).

43. Gao, C., Vo, C. D., Jin, Y. Z., Li, W. & Armes, S. P. Multihydroxy polymer-functionalized carbon nanotubes: synthesis, derivatization, and metal loading.Macromolecules 38, 8634–8648 (2005).

44. Xu, Z. & Gao, C. Graphene in macroscopic order: liquid crystals and wet-spunfibers. Acc. Chem. Res. doi:10.1021/ar4002813 (2014).

AcknowledgementsThis work is supported by the National Natural Science Foundation of China (no. 51173162and no. 21325417), Qianjiang Talent Foundation of Zhejiang Province (no. 2010R10021),Fundamental Research Funds for the Central Universities (no. 2013XZZX003) and ZhejiangProvincial Natural Science Foundation of China (no. R4110175).

Author contributionsL.K. and C.G. conceived and designed the research, analysed the experimental data andwrote the paper; C.G. supervised and directed the project. T.H., B.Z., Y.H., X.Z., K.G. andH.S. contributed to some experiments and took part in discussions.

Additional informationSupplementary Information accompanies this paper at http://www.nature.com/naturecommunications

Competing financial interests: The authors declare no competing financial interests.

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How to cite this article: Kou, L. et al. Coaxial wet-spun yarn supercapacitors forhigh-energy density and safe wearable electronics. Nat. Commun. 5:3754doi: 10.1038/ncomms4754 (2014).

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